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From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Marcel Holtmann <marcel@holtmann.org>,
	Johan Hedberg <johan.hedberg@gmail.com>,
	Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
	linux-bluetooth@vger.kernel.org
Cc: "David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>, Lin Ma <linma@zju.edu.cn>,
	netdev@vger.kernel.org
Subject: [PATCH v2] Bluetooth: call lock_sock() outside of spinlock section
Date: Wed, 7 Jul 2021 18:43:36 +0900	[thread overview]
Message-ID: <9deece33-5d7f-9dcb-9aaa-94c60d28fc9a@i-love.sakura.ne.jp> (raw)
In-Reply-To: <20210627131134.5434-1-penguin-kernel@I-love.SAKURA.ne.jp>

syzbot is hitting might_sleep() warning at hci_sock_dev_event() due to
calling lock_sock() with rw spinlock held [1]. Defer calling lock_sock()
via sock_hold().

Link: https://syzkaller.appspot.com/bug?extid=a5df189917e79d5e59c9 [1]
Reported-by: syzbot <syzbot+a5df189917e79d5e59c9@syzkaller.appspotmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Tested-by: syzbot <syzbot+a5df189917e79d5e59c9@syzkaller.appspotmail.com>
Fixes: e305509e678b3a4a ("Bluetooth: use correct lock to prevent UAF of hdev object")
---
Changes in v2:
  Take hci_sk_list.lock for write in case bt_sock_unlink() is called after
  sk_hashed(sk) test, and defer hci_dev_put(hdev) till schedulable context.

 net/bluetooth/hci_sock.c | 32 +++++++++++++++++++++++++++++---
 1 file changed, 29 insertions(+), 3 deletions(-)

diff --git a/net/bluetooth/hci_sock.c b/net/bluetooth/hci_sock.c
index b04a5a02ecf3..d8e1ac1ae10d 100644
--- a/net/bluetooth/hci_sock.c
+++ b/net/bluetooth/hci_sock.c
@@ -758,20 +758,46 @@ void hci_sock_dev_event(struct hci_dev *hdev, int event)
 
 	if (event == HCI_DEV_UNREG) {
 		struct sock *sk;
+		bool put_dev;
 
+restart:
+		put_dev = false;
 		/* Detach sockets from device */
 		read_lock(&hci_sk_list.lock);
 		sk_for_each(sk, &hci_sk_list.head) {
+			/* hci_sk_list.lock is preventing hci_sock_release()
+			 * from calling bt_sock_unlink().
+			 */
+			if (hci_pi(sk)->hdev != hdev || sk_unhashed(sk))
+				continue;
+			/* Take a ref because we can't call lock_sock() with
+			 * hci_sk_list.lock held.
+			 */
+			sock_hold(sk);
+			read_unlock(&hci_sk_list.lock);
 			lock_sock(sk);
-			if (hci_pi(sk)->hdev == hdev) {
+			/* Since hci_sock_release() might have already called
+			 * bt_sock_unlink() while waiting for lock_sock(),
+			 * use sk_hashed(sk) for checking that bt_sock_unlink()
+			 * is not yet called.
+			 */
+			write_lock(&hci_sk_list.lock);
+			if (sk_hashed(sk) && hci_pi(sk)->hdev == hdev) {
 				hci_pi(sk)->hdev = NULL;
 				sk->sk_err = EPIPE;
 				sk->sk_state = BT_OPEN;
 				sk->sk_state_change(sk);
-
-				hci_dev_put(hdev);
+				put_dev = true;
 			}
+			write_unlock(&hci_sk_list.lock);
 			release_sock(sk);
+			sock_put(sk);
+			if (put_dev)
+				hci_dev_put(hdev);
+			/* Restarting is safe, for hci_pi(sk)->hdev != hdev if
+			 * condition met and sk_unhashed(sk) == true otherwise.
+			 */
+			goto restart;
 		}
 		read_unlock(&hci_sk_list.lock);
 	}
-- 
2.18.4



  parent reply	other threads:[~2021-07-07  9:43 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-27 13:11 [PATCH] Bluetooth: call lock_sock() outside of spinlock section Tetsuo Handa
2021-06-27 14:05 ` bluez.test.bot
2021-07-07  9:43 ` Tetsuo Handa [this message]
2021-07-07 10:08   ` [v2] " bluez.test.bot
2021-07-07 18:20   ` [PATCH v2] " Luiz Augusto von Dentz
2021-07-07 23:33     ` Tetsuo Handa
2021-07-08  1:00       ` LinMa
2021-07-09 13:50         ` Tetsuo Handa
2021-07-10 13:34       ` Tetsuo Handa
2021-07-08  7:16   ` [v2] " bluez.test.bot
2021-07-13 11:27   ` [PATCH v3] " Tetsuo Handa
2021-07-13 11:57     ` [v3] " bluez.test.bot
2021-07-14 19:20     ` [PATCH v3] " Luiz Augusto von Dentz
2021-07-15  3:03       ` LinMa
2021-07-16  3:47         ` Desmond Cheong Zhi Xi
2021-07-16  4:11           ` Desmond Cheong Zhi Xi
2021-07-16 14:48             ` Tetsuo Handa
2021-07-16 15:26               ` LinMa
2021-07-17 15:41                 ` Yet Another Patch for CVE-2021-3573 LinMa
2021-07-17 15:45                   ` LinMa
2021-07-22  9:36                 ` [PATCH v3] Bluetooth: call lock_sock() outside of spinlock section Tetsuo Handa
2021-07-22  4:47               ` LinMa
2021-07-22  5:16                 ` Tetsuo Handa

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